Method of manufacturing nozzle for inkjet head

ABSTRACT

A method of manufacturing a nozzle for an inkjet head is disclosed. With the method of manufacturing a nozzle for an inkjet head, comprising (a) coating photoresist on an inkjet head structure comprising a nozzle part; (b) adjusting exposure conditions and performing exposure and developing on the nozzle part to remove a portion of the photoresist; (c) joining a hydrophobic layer onto the portion of the nozzle part where the photoresist has been removed; and (d) removing the photoresist remaining on the nozzle part, it is easy to control the depth of the hydrophobic layer to be uniform, and the depth to which the hydrophobic layer is deposited may be controlled even when the back surface of the nozzle has a complex shape, so that the uniformity and reproduction of the hydrophobicity-treated nozzles are improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 2005-75415 filed with the Korea Industrial Property Office on Aug. 17, 2005, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to a nozzle, more specifically to a nozzle for an inkjet head and a manufacturing method thereof.

2. Description of the Related Art

An inkjet printer is a device for printing operations, in which power is supplied to a pressure chamber formed within the head so that ink droplets are sprayed through nozzles. The ink sprayed through nozzles is typically sprayed in the form of droplets and for improved printing performance of the inkjet head, the ink has to be sprayed in the form of complete droplets in a stable manner.

Thus, the nozzle region of an inkjet head requires hydrophobicity treatment, where the hydrophobicity treatment allows the menisci of the ink droplets to be formed adequately.

In general, the problem of a lack of hydrophobicity in the surface of a nozzle in an inkjet head is caused by wetting, where the nozzle surface is wetted due to repeated spraying. When such wetting occurs, the ink being sprayed forms a lump with the ink wetting the surface of the nozzle, whereby the sprayed ink does not retain the form of a complete droplet and flows down. As a result, the quality of the printing is degraded, and the menisci formed after the spraying of ink droplets become unstable. Thus, to guarantee reliable inkjet printing, it is essential to provide effective hydrophobicity treatment on the nozzle surface of an inkjet head.

For the hydrophobicity treatment of an inkjet head nozzle, such methods were used in prior art as forming the nozzle by electroplating, and forming the nozzle by micro-punching and ablation processes, etc. The outlet region of a nozzle formed by the above methods is an important factor affecting the size of an ink droplet, ink spray performance, ink spray stability, and continuous spraying.

The conventional method of electroplating is to provide a semi-permanent hydrophobicity treatment on the nozzle surface of an inkjet printer head by plating with a hydrophobic material in a plating bath on which an electric field having a particular set of conditions is applied. Here, Teflon-based materials are mainly used as the hydrophobic material, representative of which is PTFE (polytetrafluoroethylene).

To perform hydrophobicity treatment on the surface of a nozzle using PTFE, a method is used of performing composite plating treatment in a plating bath on which an electric field having a particular set of conditions is applied. Since this method of hydrophobicity treatment using composite plating has no directionality, a hydrophobic layer is formed not only on the surface of the nozzle where a hydrophobic layer is desired, but also on the back surface of the nozzle where a hydrophobic layer is not desired.

Thus, when providing hydrophobicity treatment using composite plating, a preliminary process is additionally required for preventing the formation of a hydrophobic layer on the back surface of the nozzle. That is, to provide hydrophobicity treatment only on the surface of the nozzle, an insulation film was first formed on the back surface of the nozzle with a non-conductive matter and the plating of a hydrophobic layer was performed afterwards in prior art, so that a hydrophobic layer was not formed on the back surface of the nozzle.

Here, a representative material used as the insulation film is photoresist, and a method of forming an insulation film on the back surface of a nozzle is as shown in FIG. 1. FIG. 1 is a schematic diagram illustrating a method of hydrophobicity treatment on a nozzle for an inkjet head by composite plating according to prior art.

Before performing hydrophobicity treatment on the nozzle 10 as in FIG. 1, an insulation film 12 is formed on the back surface of the nozzle 10 by coating photoresist via screen printing, etc. After forming the insulation film 12, a hydrophobic layer 14 of PTFE is formed on the surface of the nozzle 10 generally by composite plating processes.

FIG. 2 is a schematic diagram illustrating a method of hydrophobic treatment on a nozzle for an inkjet head by vacuum deposition according to prior art, where the linear directionality of vacuum deposition is used to form a uniform non-conductive thin film on the back surface of the nozzle, and an overall plating of hydrophobic material is applied on the front surface of the nozzle.

Before performing hydrophobicity treatment on the front surface of the nozzle 30 as in FIG. 2, a non-conductive thin film 32 is formed on the back surface of the nozzle 30 by vacuum deposition. Teflon-based material is plated on the front surface of the nozzle 30 on which the non-conductive thin film 32 has been formed, to obtain a hydrophobic layer 34. After the hydrophobic layer 34 is formed, the nozzle 30 is heat-treated to complete the hydrophobicity treatment.

In general, the hydrophobic layer of a nozzle in an inkjet head is positioned at the inlet of the nozzle, and is formed up to several μm into the interior. With the conventional methods described above for forming a hydrophobic layer on a nozzle of an inkjet head, it is difficult to completely prevent a hydrophobic layer being deposited on the back surface of the nozzle, and it is difficult also to control the hydrophobic layer to be formed in a uniform depth into the interior of the nozzle. Thus, the sizes of the droplets may not be uniform during the spraying, with lowered reliability for repeated printing.

Also, the conventional methods described above involve complicated processes, so that it is difficult to manage the process conditions, and with these methods, the yield of nozzle plates coated for hydrophobicity treatment is low, or the degree of coating is not uniform.

With regards examples of prior art related to the hydrophobicity treatment of a nozzle for an inkjet head, firstly, the technique of forming a hydrophobic layer in a stable manner using contact printing entails the problem that it is difficult to form the hydrophobic layer in a uniform depth into the nozzle.

Secondly, for the technique of controlling the depth of the hydrophobic layer by forming an insulation film only on the back surface of the nozzle, since the depth of the hydrophobic layer is determined during the process of forming the insulation film, controlling the depth of the hydrophobic layer to be uniform is performed with low precision.

Thirdly, the technique of using photolithography is limited in that there has not yet been disclosed a process of adjusting the exposure conditions for controlling the depth of the hydrophobic layer to be uniform. That is, the prior art is limited in that the present invention cannot readily be derived, an aspect of which comprises controlling the depth of the hydrophobic layer to be uniform, by coating liquid photoresist on the entire nozzle part, adjusting the exposure conditions, and removing the photoresist layer.

SUMMARY

The present invention aims to provide a method of manufacturing a nozzle for an inkjet head, with which it is easy to control the depth of the hydrophobic layer to be uniform, as the hydrophobic layer is formed on the nozzle of the inkjet head using photolithography, and with which the deposition depth of the hydrophobic layer can be controlled to be uniform even when the back surface of the nozzle has a complex shape.

One aspect of the present invention provides a method of manufacturing a nozzle for an inkjet head, comprising (a) coating photoresist on an inkjet head structure comprising a nozzle part; (b) adjusting exposure conditions and performing exposure and developing on the nozzle part to remove a portion of the photoresist; (c) joining a hydrophobic layer onto the portion of the nozzle part where the photoresist has been removed; and (d) removing the photoresist remaining on the nozzle part.

The head structure further may comprise any one or more of a pressure chamber, an ink injection channel, and a manifold. Preferably, the photoresist may be a liquid. The exposure conditions may include exposure time or exposure amount.

The hydrophobic layer may comprise Teflon-based material or parylene. Preferably, the hydrophobic layer may be joined by vacuum deposition or by plating.

Operation (b) may further comprise adjusting the exposure conditions so that the photoresist coated on an outer surface of the nozzle part is sensitized. Operation (b) may further comprise adjusting the exposure conditions so that the photoresist is sensitized up to a predetermined depth of the nozzle. It may be preferable for the predetermined depth to be uniform along the inner perimeter of the nozzle.

Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a method of performing hydrophobicity treatment on a nozzle for an inkjet head by composite plating according to prior art.

FIG. 2 is a schematic diagram illustrating a method of hydrophobic treatment on a nozzle for an inkjet head by vacuum deposition according to prior art.

FIG. 3 is a cross-sectional view illustrating the nozzle part of a nozzle for an inkjet head.

FIG. 4 is a flowchart illustrating a method of manufacturing a nozzle for an inkjet head according to an embodiment of the present invention.

FIG. 5 is a schematic diagram illustrating a process of manufacturing a nozzle for an inkjet head according to an embodiment of the present invention.

DETAILED DESCRIPTION

Embodiments of the invention will now be described in more detail with reference to the accompanying drawings, wherein like reference numerals refer to the like elements throughout, and redundant explanations are omitted.

FIG. 3 is a cross-sectional view illustrating the nozzle part of a nozzle for an inkjet head. In FIG. 3 are illustrated a nozzle part 120 a, a nozzle hole 120, and a hydrophobic layer 141. An aspect of the present invention is for controlling the depth of the hydrophobic layer formed on the nozzle of the inkjet head to be uniform, and is characterized by using photolithography for precision control of the depth to which the hydrophobic layer is formed into the nozzle hole, as compared to conventional techniques of depositing an insulation film and afterwards plating the hydrophobic layer.

That is, as illustrated in FIG. 3, the hydrophobic layer is formed up to a predetermined depth into the nozzle hole so that the menisci of the ink droplets are formed adequately. Thus, with the present invention, photoresist is coated overall on the surface of the nozzle part, after which the exposure conditions are adjusted, such as exposure time, exposure amount, etc., to precisely adjust the degree of sensitivity of the photoresist on the outer surface of the nozzle part and inside the nozzle hole. Then, the photoresist layer is removed, and the hydrophobic layer is deposited, so that the deposition depth of the hydrophobic layer may be controlled.

FIG. 4 is a flowchart illustrating a method of manufacturing a nozzle for an inkjet head according to an embodiment of the present invention.

To form a hydrophobic layer on a nozzle for an inkjet head according to the present embodiment, first, photoresist is coated overall on the surface of the inkjet head structure (50). The nozzle part is included in the inkjet head structure, and in addition, a pressure chamber, ink injection channels, and a manifold, etc., may also be included.

An aspect of the present invention is for controlling the depth to which the hydrophobic layer is deposited by coating photoresist overall on the surface of the inkjet head structure and afterwards selectively removing the photoresist in portions where the hydrophobic layer is to be deposited. Thus, unlike in prior art, the hydrophobic layer may readily be formed uniformly even when various components of the inkjet head are already formed.

That is, according to the present invention, the same process is utilized for the case of forming the various components of the head after forming the nozzle part of the inkjet head and depositing the hydrophobic layer, and for the case of depositing the hydrophobic layer on the nozzle part while the components of the head are already formed. Thus, not only is it possible to deposit the hydrophobic layer on the nozzle part after the components of the head are already formed, but also it can be performed easily without any particular technical difficulties.

In order to thus readily coat photoresist on the head structure, it is advantageous to form a photoresist coating layer on the outer surface of the inkjet head structure by methods of overall coating, spraying, and precipitating, etc., using liquid photoresist. However, the present invention is not limited to the above methods for the method of coating photoresist, and it is to be appreciated that any method may be included that provides a coating layer evenly formed on the outer surface of the inkjet head structure, within a scope apparent to those skilled in the art.

Next, exposure and developing are performed on the nozzle part to remove portions of the photoresist (60). The photoresist is a light-sensitive material, which undergoes a change in its properties when exposed to ultraviolet rays, etc., so that it is possible to selectively remove or leave certain areas. In general, there are specified exposure conditions, such as exposure time and exposure amount, etc., established by the manufacturer for sensitizing the photoresist by a required amount.

Therefore, by exposing and developing the surface of the nozzle part under the appropriate exposure conditions, the photoresist may be selectively removed only in the portions necessary. Also, as illustrated in FIG. 3, in order to deposit the hydrophobic layer up to a predetermined depth into the nozzle, the photoresist must be removed in the nozzle up to a predetermined depth before depositing the hydrophobic layer, where this may be achieved by adjusting the exposure time or exposure amount.

The appropriate depth to which the hydrophobic layer is formed into the nozzle hole varies according to the shape of the nozzle part, and in some cases, it may be advantageous to form the hydrophobic layer only on the surface around the nozzle hole, i.e. without the hydrophobic layer formed within the nozzle hole. In such cases, the exposure conditions are adjusted so that only the photoresist coated on the outer surface of the nozzle part is sensitized.

On the other hand, in order for the hydrophobic layer to be deposited up to a predetermined depth in the end of the nozzle hole, the exposure conditions are adjusted so that the photoresist is sensitized up to the predetermined depth of the nozzle. Of course, to allow the menisci of the ink droplets to be formed adequately, the exposure conditions are adjusted so that the depth to which the photoresist is sensitized, i.e. the depth to which the hydrophobic layer is deposited, is made uniform along the inner perimeter of the nozzle.

Next, the hydrophobic layer is joined to the portions of the nozzle part where the photoresist has been removed (70). It is apparent to those skilled in the art that while the hydrophobic layer may be joined according to conventional methods such as vacuum deposition or plating, etc., a physical joining method may also be applied which can be implemented in a single photolithography process without a separate plating process, etc. As the process for joining the hydrophobic layer is apparent to those skilled in the art, detailed explanations on this matter are not provided.

As mentioned above, it is advantageous for the hydrophobic layer to comprise Teflon-based material or parylene. The material for the hydrophobic layer is also apparent to those skilled in the art, and detailed explanations on this matter are not provided.

Finally, the process of forming the hydrophobic layer on the nozzle for an inkjet is completed by removing the photoresist remaining on the nozzle part (80). The method of removing the photoresist is apparent to those skilled in the art, and detailed explanations on this matter are not provided.

FIG. 5 is a schematic diagram illustrating a process of manufacturing a nozzle for an inkjet head according to an embodiment of the present invention. In FIG. 5 are illustrated a nozzle part 120, a nozzle hole 122, photoresist 124, 124 a, and a hydrophobic layer 141.

The process of forming the hydrophobic layer 141 on the nozzle part 120 of the inkjet head according to the present embodiment will be described with reference to FIG. 5. Onto the surface of the nozzle part 120 of the inkjet head, formed such as that in (a) of FIG. 5, liquid photoresist 124 is coated overall, as in (b) of FIG. 5.

Then, taking into account the depth into the nozzle hole 122 to which the hydrophobic layer 141 will be deposited, exposure and developing are performed on the outer surface of the nozzle part 120 as in (c) of FIG. 5. The depth of the hydrophobic layer 141 of the nozzle for the inkjet head is determined during this procedure. After the photolithography process including exposure and developing, portions of the coated photoresist 124 are removed from the surface of the nozzle part 120, i.e. the portions where the hydrophobic layer 141 is to be formed.

As in (d) of FIG. 5, onto the portions of the nozzle part 120 where the photoresist 124 has been removed, i.e. the portions where the hydrophobic layer 141 is to be formed, the hydrophobic layer 141 is joined according to a method apparent to those skilled in the art. During this procedure, the hydrophobic layer 141 is formed in a necessary amount on the nozzle for the inkjet head.

Finally, as in (e) of FIG. 5, the photoresist 124a remaining on the surface of the nozzle part 120 is removed, to complete the process of forming the hydrophobic layer 141 on the nozzle for the inkjet head.

According to the present invention comprised as above, it is easy to control the depth of the hydrophobic layer to be uniform, and the depth to which the hydrophobic layer is deposited may be controlled even when the back surface of the nozzle has a complex shape, so that the uniformity and reproduction of the hydrophobicity-treated nozzles are improved. Also, since the nozzles treated for hydrophobicity are uniform, the sizes of the sprayed ink droplets are made uniform, and as the wetting phenomenon is prevented on the nozzles of an inkjet head due to the hydrophobicity treatment, the printing performance is improved.

While the spirit of the invention has been described in detail with reference to particular embodiments, the embodiments are for illustrative purposes only and do not limit the invention. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the invention. 

1. A method of manufacturing a nozzle for an inkjet head, the method comprising: (a) coating photoresist on an inkjet head structure comprising a nozzle part; (b) adjusting exposure conditions and performing exposure and developing on the nozzle part to remove a portion of the photoresist; (c) joining a hydrophobic layer onto the portion of the nozzle part where the photoresist has been removed; and (d) removing the photoresist remaining on the nozzle part.
 2. The method of claim 1, wherein the head structure further comprises any one or more of a pressure chamber, an ink injection channel, and a manifold.
 3. The method of claim 1, wherein the photoresist is a liquid.
 4. The method of claim 1, wherein the exposure conditions include exposure time or exposure amount.
 5. The method of claim 1, wherein the hydrophobic layer comprises Teflon-based material or parylene.
 6. The method of claim 1, wherein the hydrophobic layer is joined by vacuum deposition or by plating.
 7. The method of claim 1, wherein the operation (b) further comprises adjusting the exposure conditions so that the photoresist coated on an outer surface of the nozzle part is sensitized.
 8. The method of claim 1, wherein the operation (b) further comprises adjusting the exposure conditions so that the photoresist is sensitized up to a predetermined depth of the nozzle.
 9. The method of claim 8, wherein the predetermined depth is uniform along the inner perimeter of the nozzle. 